Abstract The recognition of posttranslational modifications by modular protein domains is a fundamental determinant of selectivity in signaling pathways. In particular tyrosine (Tyr) phosphorylation pathways are regulated by a large number of different, modular phosphotyrosine (pTyr) recognition domains such as SH2 and PTB domains that recognize pTyr and coordinate signaling events downstream of kinases. While in eukaryotes, several pTyr recognition domains have independently evolved and in humans, for example, there are more pTyr recognition domains than Tyr kinases, no pTyr recognition domains have been identified in bacteria. Yet, pTyr reader domains evolved repeatedly, are highly versatile, are highly integrated parts of phosphorylation pathways, and are nearly ubiquitous except in bacteria. Given the large networks of Tyr phosphorylation in bacteria, it appears likely that bacteria also evolved pTyr recognition domains that remain to be discovered. Here, we will test this idea by identifying pTyr-binding proteins in Mtb.